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Abstract:

A sanitary washing apparatus includes a washing nozzle configured to
discharge wash water toward a human body part, the washing nozzle
including: a water supply path configured to pass the wash water; an
orifice configured to direct the wash water passed through the water
supply path toward the human body part; a throat provided on a trajectory
connecting the orifice and the human body part; a mixing chamber provided
on a downstream side of the orifice and on an upstream side of the
throat, an area of a cross section of the mixing chamber perpendicular to
a discharge direction of the wash water being larger than an area of a
cross section of the orifice perpendicular to the discharge direction;
and an air intake portion configured to take air into the mixing chamber
by a negative pressure generated by wash water flowing from the orifice
toward the throat, a return flow being generated in the mixing chamber by
wash water flowing out from the orifice and having a flow direction
changed by a wall face of the mixing chamber, the air sucked into the
mixing chamber via the air intake portion being mixed into the return
flow as an air bubble, the return flow mixed with the air joining wash
water flowing from the orifice toward the throat and being discharged
from the throat.

Claims:

1. A sanitary washing apparatus comprising a washing nozzle configured to
discharge wash water toward a human body part, the washing nozzle
including: a water supply path configured to pass the wash water; an
orifice configured to direct the wash water passed through the water
supply path toward the human body part; a throat provided on a trajectory
connecting the orifice and the human body part; a mixing chamber provided
on a downstream side of the orifice and on an upstream side of the
throat, an area of a cross section of the mixing chamber perpendicular to
a discharge direction of the wash water being larger than an area of a
cross section of the orifice perpendicular to the discharge direction;
and an air intake portion configured to take air into the mixing chamber
by a negative pressure generated by wash water flowing from the orifice
toward the throat, a return flow being generated in the mixing chamber by
wash water flowing out from the orifice and having a flow direction
changed by a wall face of the mixing chamber, the air sucked into the
mixing chamber via the air intake portion being mixed into the return
flow as an air bubble, the return flow mixed with the air joining wash
water flowing from the orifice toward the throat and being discharged
from the throat.

2. The apparatus according to claim 1, wherein a repetition of increase
and decrease in pressure is caused in the mixing chamber by a negative
pressure generated by wash water flowing from the orifice toward the
throat and the air sucked into the mixing chamber via the air intake
portion.

3. The apparatus according to claim 1, wherein the orifice and the throat
are provided in an end portion of the mixing chamber as viewing a cross
section perpendicular to the discharge direction of the wash water.

4. The apparatus according to claim 1, wherein the air intake portion is
provided in a position away from the orifice and the throat.

5. The apparatus according to claim 1, wherein the air intake portion is
formed to run along a flow of the return flow, and the air sucked via the
air intake portion flows into the mixing chamber to run along the flow of
the return flow.

6. The apparatus according to claim 1, wherein the mixing chamber has a
shape configured to reduce attenuation of wash water including the air.

7. The apparatus according to claim 1, wherein a narrowing projection
configured to narrow a flow path area of the throat is provided at the
throat.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority
from the prior Japanese Patent Application No. 2010-007439, filed on Jan.
15, 2010; the entire contents of which are incorporated herein by
reference.

BACKGROUND

[0002] 1. Field of the Invention

[0003] Embodiments described herein relate generally to a sanitary washing
apparatus, and specifically to a sanitary washing apparatus that uses
water to wash the bottom and the like of a user sitting on a sit-down
toilet stool.

[0004] 2. Background Art

[0005] It is considered that a washing method that achieves both a feeling
of stimulation and a feeling of volume by wash water, for example, is
good in order to enhance the feeling of washing in a sanitary washing
apparatus. To intensify the feeling of stimulation, it is necessary, for
example, to increase the flow speed of discharged water, to cause
discharged water to hit a part of a human body without decreasing the
increased flow speed in the flow path, and the like.

[0006] Methods for increasing the flow speed of discharged water include,
for example, narrowing the diameter of the washing flow path, increasing
the flow speed compulsorily with a pump, and the like. On the other hand,
methods for causing discharged water to hit a part of a human body
without decreasing the increased flow speed in the flow path include, for
example, providing an orifice portion and a throat portion so that the
human body part may exist on a locus connecting the orifice portion and
the throat portion, and the like (JP-A 2002-167844 and JP-A 2002-188202).

[0007] Methods for increasing the feeling of volume include, for example,
making the exit area of the throat portion larger than the entry area to
generate oscillation in discharged water to discharge wash water to a
wider area of a part of a human body.

[0008] However, the apparatuses described in JP-A 2002-167844 and JP-A
2002-188202 require a larger amount of wash water. Therefore, it is
necessary for the sanitary washing apparatus to include a warm-water tank
with a larger volume in order to enable to discharge warm water even in
the case of being used over longer periods of time or the case of being
used continuously. This requires a larger amount of electricity in order
to heat the water in the warm-water tank, leading to increased standby
power of the warm-water tank. This may impede energy saving.

[0009] In contrast, energy saving can be accomplished in the case where,
for example, the sanitary washing apparatus is provided with not a
warm-water tank but an instantaneous-heating heat exchanger that can heat
supplied water instantaneously into prescribed warm water. However, as
described above, there may be cases where the instantaneous-heating heat
exchanger cannot be used in the case where a larger amount of wash water
is needed. This is because there are limitations on the flow rate at
which the instantaneous-heating heat exchanger can generate warm water.
For example, when water having a flow rate exceeding the warm-water
generation capacity of the instantaneous-heating heat exchanger is
supplied, the water supplied is not heated sufficiently at the
instantaneous-heating heat exchanger. This may cause temperature
unevenness in the generated warm water or make it impossible to generate
prescribed warm water.

SUMMARY

[0010] According to an aspect of the invention, there is provided a
sanitary washing apparatus including a washing nozzle configured to
discharge wash water toward a human body part, the washing nozzle
including: a water supply path configured to pass the wash water; an
orifice configured to direct the wash water passed through the water
supply path toward the human body part; a throat provided on a trajectory
connecting the orifice and the human body part; a mixing chamber provided
on a downstream side of the orifice and on an upstream side of the
throat, an area of a cross section of the mixing chamber perpendicular to
a discharge direction of the wash water being larger than an area of a
cross section of the orifice perpendicular to the discharge direction;
and an air intake portion configured to take air into the mixing chamber
by a negative pressure generated by wash water flowing from the orifice
toward the throat, a return flow being generated in the mixing chamber by
wash water flowing out from the orifice and having a flow direction
changed by a wall face of the mixing chamber, the air sucked into the
mixing chamber via the air intake portion being mixed into the return
flow as an air bubble, the return flow mixed with the air joining wash
water flowing from the orifice toward the throat and being discharged
from the throat.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic perspective view illustrating a toilet system
including a sanitary washing apparatus according to an embodiment of the
invention;

[0012]FIG. 2 is a schematic plan view of an end of a washing nozzle of
the embodiment as viewed from side;

[0013]FIG. 3 is a schematic plan view of the end of the washing nozzle of
the embodiment as viewed from a direction of arrow A illustrated in FIG.
2;

[0014]FIG. 4 is a schematic cross-sectional view illustrating the inner
structure of the washing nozzle of the embodiment;

[0015]FIG. 5 is a schematic cross-sectional view illustrating the inner
structure of the washing nozzle of the embodiment;

[0016]FIG. 6 is a schematic cross-sectional view for describing the flow
of wash water in the washing nozzle of the embodiment;

[0017]FIG. 7 is a schematic cross-sectional view for describing the flow
of wash water in a washing nozzle according to a variation of the
embodiment; and

[0018] FIG. 8 is a photograph illustrating an example of the wash water
discharged from the washing nozzle of the embodiment.

DETAILED DESCRIPTION

[0019] A first invention is a sanitary washing apparatus including a
washing nozzle configured to discharge wash water toward a human body
part, the washing nozzle including: a water supply path configured to
pass the wash water; an orifice configured to direct the wash water
passed through the water supply path toward the human body part; a throat
provided on a trajectory connecting the orifice and the human body part;
a mixing chamber provided on a downstream side of the orifice and on an
upstream side of the throat, an area of a cross section of the mixing
chamber perpendicular to a discharge direction of the wash water being
larger than an area of a cross section of the orifice perpendicular to
the discharge direction; and an air intake portion configured to take air
into the mixing chamber by a negative pressure generated by wash water
flowing from the orifice toward the throat, a return flow being generated
in the mixing chamber by wash water flowing out from the orifice and
having a flow direction changed by a wall face of the mixing chamber, the
air sucked into the mixing chamber via the air intake portion being mixed
into the return flow as an air bubble, the return flow mixed with the air
joining wash water flowing from the orifice toward the throat and being
discharged from the throat.

[0020] According to this sanitary washing apparatus, the wash water
flowing toward the entry of the throat is divided into wash water that
passes through the throat and wash water whose flow direction is changed
by the wall face of the mixing chamber. A return flow is produced by the
wash water whose flow direction is changed by the wall face of the mixing
chamber. A negative pressure is generated in the mixing chamber by the
return flow and the wash water flowing from the orifice toward the
throat. Accordingly, the air outside the washing nozzle is sucked into
the mixing chamber via the air intake portion. As a consequence, the air
sucked into the mixing chamber is mixed into the return flow as air
bubbles and flows along with the return flow. The return flow mixed with
the air joins the wash water flowing from the orifice toward the throat
and is discharged from the throat.

[0021] Thereby, a lot of air can be mixed into wash water jetted out from
the throat toward a human body part. This can increase water-saving
efficiency. Since water-saving efficiency can be increased, electric
power for heating the water in a warm-water tank, for example, can be
reduced to decrease standby power more. Therefore, energy saving can be
accomplished.

[0022] A second invention is the sanitary washing apparatus according to
the first invention, in which a repetition of increase and decrease in
pressure is caused in the mixing chamber by a negative pressure generated
by wash water flowing from the orifice toward the throat and the air
sucked into the mixing chamber via the air intake portion.

[0023] According to this sanitary washing apparatus, a repetition of a
high-speed portion and a low-speed portion is caused in wash water
discharged from the washing nozzle due to the repetition of increase and
decrease in pressure in the mixing chamber. In other words, a speed
difference is caused between points of the wash water discharged from the
washing nozzle. The speed difference gives rise to a repetition of
condensation and rarefaction of the wash water as a natural variation.
The speed difference of the wash water forms liquid drops in the wash
water discharged from the washing nozzle.

[0024] Therefore, the portion of liquid drops of wash water can land on a
human body part, allowing to provide a feeling of volume. Furthermore,
when the portion of liquid drops of wash water lands on a human body
part, the human body part has a larger load. This can provide a feeling
of stimulation. Therefore, a feeling of washing can be maintained even if
the flow rate of wash water is reduced, while increasing water-saving
efficiency and reducing standby power.

[0025] A third invention is the sanitary washing apparatus according to
the first invention, in which the orifice and the throat are provided in
an end portion of the mixing chamber as viewing a cross section
perpendicular to the discharge direction of the wash water.

[0026] According to this sanitary washing apparatus, since the orifice and
the throat are provided in an end portion of the mixing chamber as
viewing a cross section perpendicular to the discharge direction of wash
water, wash water flowing from the orifice toward the throat passes
through the end portion of the mixing chamber. Since a larger space in
which the return flow is produced is ensured, the return flow is formed
larger in the mixing chamber. Accordingly, pieces of the air mixed in
with the return flow come into contact with each other less readily and
are kept in a fine state. Consequently, the air sucked into the mixing
chamber and the return flow are mixed together more efficiently.
Therefore, more air is mixed into the return flow.

[0027] A fourth invention is the sanitary washing apparatus according to
the first invention, in which the air intake portion is provided in a
position away from the orifice and the throat.

[0028] According to this sanitary washing apparatus, the air sucked into
the mixing chamber is mixed into the return flow with limited influence
of disorder of the jet flow of wash water flowing from the orifice toward
the throat. Accordingly, the air sucked into the mixing chamber is mixed
into the return flow in a more stable state. Consequently, the air sucked
into the mixing chamber and the return flow are mixed together more
efficiently. Therefore, more air is mixed into the return flow.

[0029] A fifth invention is the sanitary washing apparatus according to
the first invention, in which the air intake portion is formed to run
along a flow of the return flow, and the air sucked via the air intake
portion flows into the mixing chamber to run along the flow of the return
flow.

[0030] According to this sanitary washing apparatus, since the air to be
sucked into the mixing chamber is sucked and flows to run along the flow
of the return flow, the air flows into the mixing chamber more
efficiently and is mixed into the return flow more efficiently.
Therefore, more air is mixed into the return flow.

[0031] A sixth invention is the sanitary washing apparatus according to
the first invention, in which the mixing chamber has a shape configured
to reduce attenuation of wash water including the air.

[0032] According to this sanitary washing apparatus, since the mixing
chamber has a shape configured to reduce attenuation of the return flow,
the flow of the return flow is easily maintained and is less likely to
become slow. As a consequence, the air sucked into the mixing chamber and
the return flow are mixed together yet more efficiently. Therefore, yet
more air is mixed into the return flow.

[0033] A seventh invention is the sanitary washing apparatus according to
the first invention, in which a narrowing projection configured to narrow
the flow path area of the throat is provided at the throat.

[0034] According to this sanitary washing apparatus, since the narrowing
projection configured to narrow the flow path area of the throat is
provided at the throat, the flow of water mixed with air and exiting from
the mixing chamber generates a negative pressure in the throat after
passing the narrowing projection of the throat. The negative pressure
causes a repeated movement of the flow of water being drawn to the inner
wall of the throat. Thereby, water discharged from the throat is
discharged while oscillating with a central focus on the discharge
direction of the water. Therefore, the discharged water can be turned
into a droplet state at early stage, allowing to provide a high feeling
of stimulation. Furthermore, the oscillation can extend the washing area.

[0035] Embodiments of the invention will now be described with reference
to the drawings. In the drawings, similar components are marked with like
reference numerals, and a detailed description thereof is omitted as
appropriate.

[0036] FIG. 1 is a schematic perspective view illustrating a toilet system
including a sanitary washing apparatus according to an embodiment of the
invention.

[0037] The toilet system illustrated in FIG. 1 includes a sit-down toilet
stool (hereinafter simply referred to as "toilet stool" for convenience
of description) 800 and a sanitary washing apparatus 100 provided
thereon. The sanitary washing apparatus 100 includes a casing 400, a
toilet seat 200, and a toilet lid 300. The toilet seat 200 and the toilet
lid 300 are each pivotally supported on the casing 400 in an
openable/closable manner.

[0038] A part washing functional unit that performs washing of a human
body part of a user sitting on the toilet seat 200 and the like are
installed in the casing 400. More specifically, a nozzle unit (not
illustrated) capable of washing "the bottom" and the like of a user
sitting on the toilet seat 200 are installed in the casing 400. The
not-illustrated nozzle unit includes a washing nozzle 410 that jets out
water supplied from, for example, a warm-water tank or the like toward
"the bottom" and the like of a user.

[0039] Further, a seating detection sensor 404 that detects a user's
sitting on the toilet seat 200, for example, is provided in the casing
400. In the case where the seating detection sensor 404 is detecting a
user sitting on the toilet seat 200, the user can operate an operating
unit, such as a not-illustrated remote control, to move the washing
nozzle 410 into a bowl 801 of the toilet stool 800. FIG. 1 illustrates
the sanitary washing apparatus 100 in a state in which the washing nozzle
410 has been moved into the bowl 801.

[0040]FIG. 2 is a schematic plan view of an end of the washing nozzle of
this embodiment as viewed from side.

[0041]FIG. 3 is a schematic plan view of the end of the washing nozzle of
this embodiment as viewed from the direction of arrow A illustrated in
FIG. 2.

[0042] As illustrated in FIG. 2 and FIG. 3, one or a plurality of water
discharge ports 418 are provided at the end of the washing nozzle 410.
The washing nozzle 410 can jet out water through the water discharge port
418 provided at the end thereof to wash a human body part of a user
sitting on the toilet seat 200. In the specification of this application,
"water" includes not only cold water but also heated water. An air intake
port 421 through which air can be taken into the washing nozzle 410 is
provided at the end of the washing nozzle 410.

[0043]FIG. 4 and FIG. 5 are schematic cross-sectional views illustrating
the inner structure of the washing nozzle of this embodiment.

[0044]FIG. 4 is a schematic cross-sectional view taken along cut plane
B-B illustrated in FIG. 3.

[0045]FIG. 5 is a schematic cross-sectional view taken along cut plane
C-C illustrated in FIG. 3.

[0046] A water supply path 411, an orifice 413, a mixing chamber 415, a
throat 417, an air intake portion 423 are provided in the washing nozzle
410. The water supply path 411 is configured to pass wash water for
washing a human body parts.

[0047] The flow of wash water in the washing nozzle 410 is outlined as
follows. Wash water passed through the water supply path 411 passes
through the orifice 413 into the mixing chamber 415 as indicated by the
arrows illustrated in FIG. 4 and FIG. 5. Then, the water guided into the
mixing chamber 415 passes through the throat 417 and is jetted out from
the water discharge port 418 toward a human body part of a user sitting
on the toilet seat 200. In other words, one end of the throat 417
functions as the water discharge port 418. The flow of wash water is
described below.

[0048] The orifice 413 is connected to the water supply path 411 and can
increase the flow speed of water supplied from the water supply path 411.
The exit of the orifice 413 is directed to the human body part.

[0049] The mixing chamber 415 is connected with the exit of the orifice
413 and has a prescribed space. More specifically, as illustrated in FIG.
4 and FIG. 5, the area of the mixing chamber 415 in a cross section
perpendicular to the discharge direction of wash water is larger than the
area of the orifice 413 in a cross section perpendicular to the discharge
direction of wash water.

[0050] The throat 417 is provided on a trajectory connecting the orifice
413 and the human body part. The entry of the throat 417 is connected
with the mixing chamber 415. In other words, the mixing chamber 415 is
provided on a downstream side of the orifice 413 and on an upstream side
of the throat 417. The water supply path 411 and the mixing chamber 415
are connected via the orifice 413, and the mixing chamber 415 and the
exterior of the washing nozzle 415 are connected via the throat 417. A
narrowing projection 417a is provided near the entry of the throat 417,
and the area of the exit of the throat 417 is larger than the area of the
entry thereof, as illustrated in FIG. 4 and FIG. 5.

[0051] Further, the mixing chamber 415 and the exterior of the washing
nozzle 410 are connected via the air intake portion 423. The air intake
portion 423 can take air outside the washing nozzle 410 into the washing
nozzle 410. At this time, one end of the air intake portion 423 functions
as the air intake port 421. The flow of air taken into the mixing chamber
415 via the air intake portion 423 is described in detail later.

[0052] Next, the flow of wash water and the flow of air will now be
described with reference to the drawings.

[0053]FIG. 6 is a schematic cross-sectional view for describing the flow
of wash water in the washing nozzle of this embodiment.

[0054]FIG. 7 is a schematic cross-sectional view for describing the flow
of wash water in a washing nozzle according to a variation of this
embodiment.

[0056] Wash water passed through inside the water supply path 411 passes
through the orifice 413 into the mixing chamber 415 as indicated by arrow
W1 illustrated in FIG. 6. Subsequently, the wash water guided into the
mixing chamber 415 flows toward the entry of the throat 417. At this
time, as described above regarding FIG. 4 and FIG. 5, the area of the
mixing chamber 415 in a cross section perpendicular to the discharge
direction of wash water is larger than the area of the orifice 413 in a
cross section perpendicular to the discharge direction of wash water. The
change in cross-sectional area causes a negative pressure in the mixing
chamber 415, giving rise to a disorder in the jet flow of the wash water
that has passed through the orifice 413 and been introduced into the
mixing chamber 415.

[0057] The disorder of the jet flow divides the wash water flowing toward
the entry of the throat 417 into wash water that passes through the
throat 417, as indicated by arrow W2 illustrated in FIG. 6, and wash
water whose flow direction is changed by a wall face 415a of the mixing
chamber 415, as indicated by arrows W3 and W7 illustrated in FIG. 6. As a
consequence, compulsory convection flowing in certain directions is
generated in the mixing chamber 415, as indicated by arrows W3 to W8
illustrated in FIG. 6, by the wash water whose flow direction is changed
by the wall face 415a of the mixing chamber 415 and the wash water
flowing from the orifice 413 toward the throat 417.

[0058] The convection and the wash water flowing from the orifice 413
toward the throat 417 causes a negative pressure in the mixing chamber
415. Therefore, air outside the washing nozzle 410 is sucked into the
mixing chamber 415 via the air intake portion 423 as indicated by arrow
A1 illustrated in FIG. 6. As a consequence, the air sucked into the
mixing chamber 415 is mixed into the wash water of the convection
generated in the mixing chamber 415 as air bubbles and flows along with
the convection.

[0059] The wash water mixed with air comes close to the wash water flowing
from the orifice 413 toward the throat 417 as indicated by arrows W6 and
W8 illustrated in FIG. 6. Here, a negative pressure is generated around
the wash water flowing from the orifice 413 toward the throat 417.
Accordingly, at least part of the wash water mixed with air is drawn into
and joins the wash water flowing from the orifice 413 toward the throat
417. Then, the joined wash water flows toward the entry of the throat
417, with air therein. In other words, the compulsory convection
generated in the mixing chamber 415 forms a return flow that once
separates from the wash water flowing from the orifice 413 toward the
throat 417, then takes in air, and then joins the wash water.

[0060] Here, the air intake portion 423 is provided in a position away
from the orifice 413 and the throat 417 as illustrated in FIG. 6.
Therefore, air sucked into the mixing chamber 415 flows into the mixing
chamber 415 in a position away from the wash water flowing from the
orifice 413 toward the throat 417. The air flowing into the mixing
chamber 415 is mixed into the return flow as air bubbles, as described
above.

[0061] Therefore, the air sucked into the mixing chamber 415 is mixed into
the return flow with limited influence of disorder of the jet flow of the
wash water flowing from the orifice 413 toward the throat 417.
Accordingly, the air sucked into the mixing chamber 415 is mixed into the
return flow in a more stable state. Consequently, the air sucked into the
mixing chamber 415 and the return flow are mixed together more
efficiently. Thus, more air is mixed into the return flow.

[0062] Furthermore, as illustrated in FIG. 6, the air intake portion 423
is formed to run along the flow of the return flow in the upper end
portion of the mixing chamber 415. Therefore, air to be sucked into the
mixing chamber 415 is sucked and flows to run along the flow of the
return flow. Consequently, the air sucked into the mixing chamber 415
flows into the mixing chamber 415 more efficiently and is mixed into the
return flow more efficiently. Thus, more air is mixed into the return
flow.

[0063] In the invention, the air intake portion 423 may be provided in
another position in the mixing chamber 415, not limited to the upper end
portion of the mixing chamber 415. However, the direction of the air
intake portion 423 is preferably directed in the tangent direction of the
return flow. This makes it difficult for the return flow to flow out
through the air intake portion 423, and offers no obstruction to the
suction of air into the mixing chamber 415. Thus, air can be mixed into
the return flow similarly efficiently.

[0064] Furthermore, as illustrated in FIG. 6, the orifice 413 and the
throat 417 are provided not in the central portion but in an end portion
of the mixing chamber 415 as viewing a cross section perpendicular to the
discharge direction of wash water. Accordingly, the wash water flowing
from the orifice 413 toward the throat 417 passes through the end portion
of the mixing chamber 415. This ensures a larger space in which the
return flow is generated. Therefore, the return flow is formed larger in
the mixing chamber 415. Furthermore, the mixing chamber 415 has a space
large enough to allow the return flow to be formed larger. More
specifically, the distance between the wall face 415a and a wall face
415b of the mixing chamber 415 is large enough to allow the return flow
to be formed larger. Therefore, there are fewer occasions when pieces of
air mixed in with the return flow come into contact with each other, and
the air is kept in a state of fine air bubbles. Consequently, the air
sucked into the mixing chamber 415 and the return flow are mixed together
more efficiently. Thus, more air is mixed into the return flow.

[0065] Moreover, as illustrated in FIG. 6, a recess 415d is formed in at
least part of the wall face 415a of the mixing chamber 415 of this
embodiment. By forming the recess 415d, air outside the washing nozzle
410 can be sucked more stably into the mixing chamber 415 via the air
intake portion 423.

[0066] A more specific description is given as follows. At least part of
wash water whose flow direction is changed by the wall face 415a of the
mixing chamber 415 and flowing toward the air intake portion 423 goes
toward the recess 415d as indicated by arrow W10 illustrated in FIG. 6.
The flow direction of wash water going toward the recess 415d is changed
to the lower portion of the mixing chamber 415 by the recess 415d. The
wash water whose flow direction is changed to the lower portion of the
mixing chamber 415 does not flow toward the opening of the air intake
portion 423 in the mixing chamber 415. This decreases the possibility
that the opening of the air intake portion 423 in the mixing chamber 415
may be blocked by wash water. Thereby, air outside the washing nozzle 410
is sucked more stably into the mixing chamber 415 via the air intake
portion 423.

[0067] In other words, water flowing not along the return flow may prevent
air from being sucked via the air intake portion 423. The flow direction
of the water is changed by the contact with the recess 415d. This creates
a situation in which air is easily sucked via the air intake portion 423.
Thereby, air outside the washing nozzle 410 is sucked more stably into
the mixing chamber 415 via the air intake portion 423.

[0068] Thus, the recess 415d changes the flow of the return flow to
prevent the opening in the mixing chamber 415 from being blocked by
water, and thereby mixing of air can be stably supplied near the air
intake portion 423 by a negative pressure due to the return flow. This
enables more air to be mixed into the return flow as air bubbles.
Furthermore, the recess 415d can ensure a larger space in which the
return flow is generated. Therefore, there are fewer occasions when
pieces of air mixed in with the return flow come into contact with each
other, and the air is kept in a state of fine air bubbles. Consequently,
the air sucked into the mixing chamber 415 and the return flow are mixed
together more efficiently. Thus, more air is mixed into the return flow.

[0069] The means for generating a negative pressure due to the return flow
more stably is not limited to the recess 415d. It is sufficient that the
means for generating a negative pressure due to the return flow more
stably has a structure not inhibiting generation of a negative pressure.
For example, a rib provided at the opening on the mixing chamber 415 side
of the air intake portion 423 may be used.

[0070] In this embodiment, the air intake portion 423 is placed in the
upper end portion of the mixing chamber 415. This facilitates ensuring a
region with no water near the air intake portion 423 of the mixing
chamber 415. Thereby, since air easily enters the mixing chamber 415, the
air is mixed efficiently into the mixing chamber 415.

[0071] Here, in the case where, for example, the mixing chamber 415 has a
curved surface 415c formed by a larger radius as illustrated in FIG. 7,
wash water including air is difficult to attenuate. Therefore, in the
case where the mixing chamber 415 has a shape configured to reduce
attenuation of wash water including air, the flow of the wash water is
easily maintained and is less likely to become slow. As a consequence,
the air sucked into the mixing chamber 415 and the return flow are mixed
together yet more efficiently. Thus, yet more air is mixed into the
return flow.

[0072] Referring to FIG. 6 again, the return flow mixed with air joins the
wash water flowing from the orifice 413 toward the throat 417 and passes
through the throat 417 as indicated by arrows W2 and W9 illustrated in
FIG. 6. Here, a portion containing a larger amount of air mixed in wash
water as air bubbles contains a smaller amount of water mixed in the
mixing chamber 415. Therefore, the speed of the wash water in the portion
is higher. On the other hand, a portion containing a smaller amount of
air mixed in wash water as air bubbles contains a larger amount of water
mixed in the mixing chamber 415. Therefore, the speed of the wash water
in the portion is lower. This gives rise to a repetition of a high-speed
portion and a low-speed portion in wash water discharged from the water
discharge port 418. In other words, a speed difference is caused between
points of the wash water discharged from the water discharge port 418.

[0073] Otherwise, when wash water mixed with air passes through the throat
417, since the narrowing projection 417a is provided at the throat 417 on
the mixing chamber 415 side, a negative pressure is generated in the
throat 417 by the flow of the confluent water of the water to be jetted
out from the throat 417 and the return flow mixed with air bubbles after
the confluent water passes the narrowing projection 417a. The negative
pressure in the jet hole causes a repeated movement of the water flow
being drawn to the inner wall of the throat 417. Accordingly, water
discharged from the throat 417 is discharged while oscillating with a
central focus on the discharge direction thereof. Therefore, the
discharged water can be turned into a droplet state at early stage,
allowing to provide a high feeling of stimulation. Furthermore, the
oscillation can widen the washing area.

[0074] Due to such disorder of the jet flow, the wash water passing
through the throat 417 and the wash water discharged from the water
discharge port 418 oscillate as indicated by the alternate long and two
short dashes lines illustrated in FIG. 6.

[0075] Furthermore, due to such disorder of the jet flow and mixing of
air, the wash water passing through the throat 417 and the wash water
discharged from the water discharge port 418 become thin or thick. The
repetition of thinness and thickness of wash water causes a repetition of
a high-speed portion and a low-speed portion in the wash water discharged
from the water discharge port 418. In other words, a speed difference is
caused between points of the wash water discharged from the water
discharge port 418. The speed difference gives rise to a repetition of
condensation and rarefaction of wash water as a natural variation.

[0076] Otherwise, as described above, the negative pressure generated in
the mixing chamber 415 causes air outside the washing nozzle 410 to be
sucked into the mixing chamber 415 via the air intake portion 423. As a
consequence, the interior of the mixing chamber 415 changes from a
negative pressure to a positive pressure. At this time, since wash water
continuously flows from the orifice 413 toward the throat 417, a negative
pressure is generated again in the mixing chamber 415. Such a repetition
of increase and decrease of the pressure in the mixing chamber 415 causes
a repetition of a high-speed portion and a low-speed portion in the wash
water discharged from the water discharge port 418. In other words, a
speed difference is caused between points of the wash water discharged
from the water discharge port 418.

[0077] Owing to the oscillation and speed difference of the jet flow of
wash water, the wash water discharged from the water discharge port 418
changes from a continuous flow to a droplet state at early stage after
water discharge.

[0078] Furthermore, since water-saving efficiency can be increased,
electric power for heating the water in a warm-water tank, for example,
can be reduced to decrease standby power. Therefore, energy saving can be
accomplished. Furthermore, since water-saving efficiency can be
increased, an instantaneous-heating heat exchanger that can heat supplied
water instantaneously into prescribed warm water can be used, instead of
a warm-water tank. This can further accomplish energy saving.

[0079] Furthermore, according to this embodiment, liquid drops are formed
in wash water discharged from the water discharge port 418. Therefore,
the portion of liquid drops of wash water can land on a human body part,
allowing to provide a feeling of volume. Here, in the specification of
this application, the "feeling of volume" refers to being hit by
discharged water having a large water discharge cross-sectional area
(weight) and a sufficient force, in other words, a feeling of contacting
a thick water flow. Generally, the larger the water landing area of
discharged water is, the more a user feels a feeling of volume.

[0080] Moreover, when the portion of liquid drops of wash water lands on a
human body part, the human body part has a larger load. The interval of
the time when the portion of liquid drops of wash water lands on the
human body part, that is, the time interval of the repetition of
condensation and rarefaction of wash water, is short enough for the human
body not to sense. Therefore, the user feels as if liquid drops hit the
human body part continuously. Thus, a feeling of stimulation can be
provided. Here, in the specification of this application, the "feeling of
stimulation" refers to rapid discharged water hitting a human body part,
in other words, a feeling of stimulation close to a pain. The feeling of
stimulation depends on the flow speed.

[0081] Therefore, this embodiment can maintain a feeling of washing even
if the flow rate of wash water is reduced, while increasing water-saving
efficiency and reducing standby power. The feeling of washing is a
feeling expressed by the feeling of volume and the feeling of stimulation
described above.

[0082] FIG. 8 is a photograph illustrating an example of the wash water
discharged from a washing nozzle of this embodiment.

[0083] The inventors verified the water discharge state using the washing
nozzle of this embodiment formed with a mold. FIG. 8 shows a photograph
of an example of the water discharge state. Generally, a human body part
of a user sitting on the toilet seat 200 exists in a position away from
the water discharge port 418 of the washing nozzle 410 by about 50
millimeters, for example. Therefore, the human body part of the user
sitting on the toilet seat 200 exists near a position corresponding to
the value "150" shown in FIG. 8.

[0084] According to the water discharge state shown in FIG. 8, it is found
out that liquid drops of wash water are formed near the position (the
position corresponding to the value "150" shown in FIG. 8) in which it is
assumed that the human body part of the user sitting on the toilet seat
200 exists. Furthermore, according to the water discharge state shown in
FIG. 8, a lot of air is mixed in the wash water discharged from the water
discharge port 418 as air bubbles.

[0085] According to this embodiment as described above, a lot of air can
be mixed into wash water jetted out from the water discharge port 418
toward a human body part; therefore, water-saving efficiency can be
increased more. Furthermore, since water-saving efficiency can be
increased, standby power can be reduced. Therefore, energy saving can be
accomplished. Furthermore, liquid drops are formed in wash water
discharged from the water discharge port 418. Therefore, the portion of
liquid drops of wash water can land on a human body part to provide a
feeling of volume. Moreover, when the portion of liquid drops of wash
water lands on a human body part, the human body part has a larger load.
This can provide a feeling of stimulation. Therefore, a feeling of
washing can be maintained even if the flow rate of wash water is reduced,
while increasing water-saving efficiency and reducing standby power.

[0086] Hereinabove, embodiments of the invention are described. However,
the invention is not limited to these descriptions. One skilled in the
art may perform appropriately design modifications on the embodiments
described above. Such modifications also are included in the scope of the
invention to the extent that the purport of the invention is included.
For example, the shape, dimension, material, arrangement, and the like of
components of the washing nozzle 410 and the like, the installation
configuration of the orifice 413, the mixing chamber 415, and the throat
417, and the like are not limited to those illustrated but may be
appropriately altered.

[0087] Furthermore, components of the embodiments described above may be
combined within the extent of technical feasibility; and combinations of
them also are included in the scope of the invention to the extent that
the purport of the invention is included.